mksquashfs: add -verbose_action_file as synonym for -vaf

Signed-off-by: Phillip Lougher <phillip@squashfs.org.uk>
diff --git a/squashfs-tools/mksquashfs.c b/squashfs-tools/mksquashfs.c
index 7c4b6e3..a097f89 100644
--- a/squashfs-tools/mksquashfs.c
+++ b/squashfs-tools/mksquashfs.c
@@ -5240,9 +5240,11 @@
 			if(read_action_file(argv[i], 0) == FALSE)
 				exit(1);
 
-		} else if(strcmp(argv[i], "-vaf") == 0) {
+		} else if(strcmp(argv[i], "-verbose_action_file") == 0 ||
+				strcmp(argv[i], "-vaf") ==0) {
 			if(++i == argc) {
-				ERROR("%s: -vaf missing filename\n", argv[0]);
+				ERROR("%s: %s missing filename\n", argv[0],
+							argv[i - 1]);
 				exit(1);
 			}
 			if(read_action_file(argv[i], 1) == FALSE)